#include <fstream>
#include <algorithm>
#define NMAX 200000
#define MMAX 400000

using namespace std;
ifstream fin ("apm.in");
ofstream fout ("apm.out");

struct Muchie {int x,y,c;};
Muchie G[MMAX];
int n,m,cost;
int conex[NMAX];
int A[NMAX]; ///indicii muchiilor selectate in arbore
///conex[i]=comp conexa din care face parte i
void citire();
void kruskal();
void afisare();
void sortare();
bool compar(Muchie a, Muchie b)
///returneaza 1 daca muchia a trebuie sa fie inaintea muchiei b in sortare
{
    return a.c<b.c;
}

int main()
{
    citire();
    kruskal();
    afisare();
    return 0;
}

void citire()
{
    int i;
    fin>>n>>m;
    for (i=1;i<=m;i++)
         fin>>G[i].x>>G[i].y>>G[i].c;
}

void kruskal()
{
    int i,j,cx,cy,nrsel;
    ///ordonez muchiile crescator dupa cost
    ///sortare();
    sort(G+1, G+m+1, compar);
    for (i=1;i<=n;i++) conex[i]=i;
    nrsel=0;
    i=1;
    while (nrsel<n-1)
      {
        if(conex[G[i].x]!=conex[G[i].y])///nu se regasesc in aceeasi comp conexa=>nu form cicluri, deci e bine
         {
           nrsel++;
           A[nrsel]=i;
           cost+=G[i].c;
           ///unificam componentele conexe ale extremitatilor
           cx=conex[G[i].x];
           cy=conex[G[i].y];
           for (j=1;j<=n;j++)
                if (conex[j]==cy) conex[j]=cx;
         }
           i++;
    }
}
void sortare()
{
    int schimb,i;
    Muchie aux;
    do
    {
        schimb=0;
        for (i=1;i<m;i++)
            if(G[i].c>G[i+1].c)
        {
            aux=G[i]; G[i]=G[i+1]; G[i+1]=aux;
            schimb=1;
        }

    }
    while (schimb);
}
void afisare()
{
    int i;
    fout<<cost<<'\n';
    for (i=1;i<n;i++)
         fout<<G[A[i]].x<<' '<<G[A[i]].y<<'\n';
    fout.close();
}